The present invention relates to an automatic assembly system, and more particularly to an automatic assembly system which automatically mounts parts onto predetermined positions of a printed circuit board at high positional accuracy.
In an automatic assembly system which mounts parts onto predetermined positions of a circuit board in predetermined locations, if the supply error of the part to a part holder for transporting the part to the mounting position is sufficiently smaller than the allowable error range of the mounting position, the purpose can be achieved by the simple control operation of moving the holder to a target position in accordance with a predetermined numerical value after the part has been supplied. However, in the case of assembly operations in which electronic parts, e.g., ICs and LSIs, having large numbers of fine leads at very small intervals are precisely mounted onto minute wiring terminals on a printed circuit board as formed in correspondence with the leads, the extent of a positional deviation allowed between each lead and the corresponding wiring terminal is very small, and hence, it is extremely difficult that the supply error of the part from a feeder to the holder be maintained within a range permitting the aforementioned simple control. Especially in the case of mounting onto the printed circuit board the LSI whose package has a plurality of leads on its each edge, the allowable range of the lengthwise positional deviation of the lead is restricted by the width of the lead extending in the direction orthogonal thereto, and hence, the extent of dispersion allowed for the supply of the part to the holder is very severe. When it is intended to realize the allowable supply, the parts feeder and the holder become complicated and expensive. Moreover, according to such system, the application to the automatic assembly of a plurality of sorts of parts having different dimensions and shapes is difficult.